It is well known that radial tires are excellent in high speed running performance because a rigid belt is disposed outside the carcass crown portion such that the tread rigidity is increased. Further, the belt decreases a load on the carcass, which makes it possible to reduce the number of the carcass plies.
When making a conventional radial tire, as shown in FIG. 7, a carcass ply strip (a) is wound in a cylindrical shape on a former F, and the terminal edge 2 of the winding is overlapped with the starting edge 1 thereof to connect or joint thereto. In the finished tire, as shown in FIG. 8, this overlap-joint part (A) extends in the radial direction along the carcass cords. As a result, when the tire is inflated, a so called "joint-dent", a phenomenon that the outer surface of the sidewall portion dents along the overlap-joint part (A), is caused. In particular, if the joint-dent exceeds 0.4 mm, the tire appearance, durability, uniformity and the like are greatly deteriorated. Further, the dent is remarkable when the number of the carcass plies is small, especially when the carcass consists of a single ply, thereby a tire weight reduction can be hindered.
If the width of the overlap-joint part (A) is decreased to reduce the joint-dent, the carcass ply opens at the overlap-joint part (A) during shaping of the carcass, and the prevention of the opening necessitates an overlapping of at least two to four carcass cords.